Dental study of ancient chewing gum informs about oral microbiomes of the past

Artistic reconstruction of the woman who chewed the birch pitch. She has been named Lola. Illustration by Tom Björklund.

Researchers from Denmark have succeeded in extracting a complete human genome from a thousands-of-years old ‘chewing gum’. According to the researchers who published their findings in Nature Communications, it is a new untapped source of ancient DNA.

Though its popularity and constituent ingredients have changed over time, chewing gum has been used by humans for thousands of years. When researchers from the University of Copenhagen analysed a 5,700-year-old piece of chewing gum made from birch bark pitch, they succeeded in extracting a complete human genome from the pitch.

The pitch was found during archaeological excavations carried out by the Museum Lolland-Falster at Syltholm in southern Denmark.

Radiocarbon dating of the pitch helped to place it as a specimen from the early Neolithic period in Denmark, while DNA sequencing revealed that it was chewed by a female who was more closely genetically related to the hunter-gatherers of mainland Europe than to those who populated central Scandinavia at the time. It was found that she probably possessed dark skin, dark hair and blue eyes.

Traces of hazelnut and duck DNA were also identified in the pitch, suggesting that these may have formed part of the individual’s diet. The researchers also successfully identified DNA fragments from several bacterial and viral taxa, including the Epstein–Barr virus, which can cause glandular fever.

“We managed to extract many different bacterial species that are characteristic of an oral microbiome,” Dr Hannes Schroeder said.

“Our ancestors lived in a different environment and had a different lifestyle and diet, and it is therefore interesting to find out how this is reflected in their microbiome.”

Though a considerable amount of information can be uncovered through the DNA sequencing of pitch, several questions still remain—including the question of what the purpose of chewing it was. Some researchers have suggested that it may have been a method for making the pitch more pliable for further toolmaking purposes, while medicinal and hunger-suppressing uses have also been put forward for consideration.